The present invention relates to the field of security gate driving mechanism, and more specifically to a method and apparatus for sensing the gate position of a gate being driven by such a gate driving mechanism.
It is well known to operate a security gate with some form of motorized driving unit, which can be of a linear or non-linear nature. Typically such a security gate driving mechanism is operated by some form of driving mechanism controller, which, e.g., can control the speed at which the gate moves, vary the speed at which the gate moves during various stages of such movement, stop the gate and/or reverse the gate is the gate is prevented from moving the full extent of its expected movement while the driving mechanism is moving the gate in such direction, etc. Such driving mechanisms in the past have been known to receive input which can more or less grossly position the gate in incremental positions along its movement, such as by the use of limit switches associated with movement of the driving mechanism. For example in a linear driving mechanism, which may be driven, for example, by a worm gear and a carriage threadedly engaging the worm gear, movement of the carriage past certain locations on the travel of the carriage along the worm gear may be sensed by engagement of the carriage with limit switches each placed in a predetermined position along the travel of the carriage, e.g., xc2xc, xc2xd, xc2xe travel points along the full course of movement of the carriage along the worm gear. Similarly, it has been known to sense the position of the gate by, e.g., sensing the position of a hinge mechanism or a portion of a hinge mechanism, with respect to a fixed point to which the gate is swingingly attached, or the angle of a linear drive mechanism with respect to a fixed point in relation to a fixed object to which the gate is swinglingly attached.
These systems, while effective to a degree, suffer from the problem that over time or from time to time the positioning of the driving mechanism is not really representative of the true position of the gate being driven. For example, heat or cold or wear over time can modify the way that the driving mechanism works and/or the travel of the driving mechanism vis-a-vis the positioning of the gate. The driving mechanism, e.g., can become slightly bent or warped, slightly elongated or shortened. In such cases, the position of the gate calibrated to specific locations of limit switches, or calibrated to a specific angle of a driving mechanism relative to some fixed axis of rotation, etc. may not continue to accurately reflect the position of the gate, with respect, e.g., to its fully open or fully shut positions, or other positions along the way, where, e.g., the controller for the security gate driver mechanism is set to alter the speed at which the gate is being driven in one fashion or another. There exists, therefore, a need for a more continuous and precise measurement of the position of the drive mechanism which can be utilized by the security gate drive mechanism, along with other input as to the actual position of the gate to more accurately and safely control the operation of the security gate.
A method and apparatus for operating a security gate, is disclosed which may comprise a driving member connected to the security gate and adapted to move the security gate from a first position to a second position, responsive to operation of the driving mechanism; a position detection device associated with the operating mechanism and adapted to determine a first distance of the driving mechanism from a first reference point and a second distance of the driving mechanism from a second reference point, and to determine the position of the security gate based upon the relation between the first distance and the second distance. The apparatus and method may have the first reference point being the position of the position detector and the second reference point being at a preselected distance from the position detector. The apparatus and method, further, may have the position detector be an ultrasound, radio frequency or light wave, or the like, transmitter/receiver, and the first distance may be is measured by reflecting waves from a moving target moving as does the driving member and the second distance is measured by reflecting waves from a fixed target fixed in relationship to the transmitter/receiver.